ENSO-neutral continued in August 2025, with near-to-below average sea surface temperatures (SSTs) observed across the central and eastern equatorial Pacific Ocean [Fig. 1]. The latest weekly Niño SST index values ranged from -0.4°C to -0.2°C [Fig. 2]. Negative subsurface temperature anomalies (averaged from 180°-100°W) strengthened [Fig. 3], with below-average temperatures prevailing from the surface to 200m depth in the central and eastern Pacific [Fig. 4]. Low-level wind anomalies were easterly across most of the equatorial Pacific, while upper-level wind anomalies were westerly over the western and eastern equatorial Pacific. Convection was enhanced over Indonesia and was suppressed near the Date Line [Fig. 5]. Collectively, the coupled ocean-atmosphere system reflected the continuation of ENSO-neutral.

The IRI multi-model predictions slightly favor ENSO-neutral through the Northern Hemisphere winter 2025-26 [Fig. 6]. However, all available models from the North American Multi-Model Ensemble favor La Niña to emerge and persist through the winter. Based on this guidance and recently observed trends across the surface and subsurface equatorial Pacific, the team also favors La Niña to develop. In summary, a transition from ENSO-neutral to La Niña is likely in the next couple of months, with a 71% chance of La Niña during October - December 2025. Thereafter, La Niña is favored but chances decrease to 54% in December 2025 - February 2026 [Fig. 7].